1. Field of the Invention
The present invention relates to a water-repellent and oil-repellent composition useful as a coating agent for modifying a surface of a substance, and a water-repellent film formed by using the water-repellent and oil-repellent composition.
2. Description of the Related Art
A fluorine-containing alkoxy silane compound having a perfluoroalkyl group (which may hereinafter be referred to as “Rf group”) has been widely used as a coating agent for surface modification because the compound has water repellency and oil repellency derived from a fluorine atom.
A fluorine-containing alkoxy silane compound having an Rf group having 8 or more carbon atoms synthesized by telomerization has heretofore been mainly used as a fluorine-containing alkoxy silane compound to be used in a surface modification application. However, it has been reported that the fluorine-containing alkoxy silane compound having an Rf group having 8 or more carbon atoms is decomposed or metabolized in a living organism to produce perfluorooctanoic acid (hereinafter sometimes referred to as “PFOA”) showing bioaccumulative property (Japanese Patent Application Laid-Open No. 2012-219217). Accordingly, in the United States, a project for reducing the amounts of PFOA, analogues thereof, and precursors thereof to be discharged to the environment as well as their contents in products has been progressed. Therefore, in the present circumstances, it is inevitable to refrain from producing or using the fluorine-containing alkoxy silane compound having an Rf group having 8 or more carbon atoms.
A fluorine-containing alkoxy silane compound having an Rf group having 6 or less carbon atoms or fluorine-containing alkoxy silane compound having a perfluorooxyalkylene group that has low risk to a living organism and an environment has been proposed as an alternative to the fluorine-containing alkoxy silane compound having an Rf group having 8 or more carbon atoms.
Specifically, it has been proposed that a fluorine-containing compound which has an Rf group having 5 or less carbon atoms and in which the Rf group is bonded to an alkoxysilyl group through a linking group be used as a material for forming an alternate line-shaped pattern (Japanese Patent No. 4325555).
Further, it has been proposed that a composition containing, as an essential component, a fluorine compound which has a fluorine-containing group having an Rf group having 1 to 6 carbon atoms and in which the fluorine-containing group is bonded to an alkoxysilyl group through a linking group be used as a liquid-repellent surface treatment agent for photolithography (Japanese Patent Application Laid-Open No. 2008-15084).
Further, it has been proposed that a composition containing a fluorine compound which has an Rf group having 1 to 5 carbon atoms and in which the Rf group is bonded to an alkoxysilyl group through a linking group be used as a surface treatment agent for a substrate (Japanese Patent Application Laid-Open No. 2006-291266).
However, when such a fluorine-containing alkoxy silane compound having an Rf group having 6 or less carbon atoms as described in the foregoing is used as a coating agent for forming a water-repellent film, water repellency of the formed water-repellent film has not been at a sufficiently satisfactory level.